Valve Guide Loose in Head - Options?
Discussion
I really would find that very difficult to say
Perhaps 20 hours hard track use per year?
Plus a fair amount of driving on road
By the way, is it standard practice to shim valve spring seats to equalise spring force?
Certainly looks quite awkward to do, it will be interesting to see what shims come off when I get the heads back
Perhaps 20 hours hard track use per year?
Plus a fair amount of driving on road
By the way, is it standard practice to shim valve spring seats to equalise spring force?
Certainly looks quite awkward to do, it will be interesting to see what shims come off when I get the heads back
ukkid35 said:
I really would find that very difficult to say
Perhaps 20 hours hard track use per year?
Plus a fair amount of driving on road
By the way, is it standard practice to shim valve spring seats to equalise spring force?
Certainly looks quite awkward to do, it will be interesting to see what shims come off when I get the heads back
yes you should always shim spring seats to ensure spring seat pressure is correct for all valves.Perhaps 20 hours hard track use per year?
Plus a fair amount of driving on road
By the way, is it standard practice to shim valve spring seats to equalise spring force?
Certainly looks quite awkward to do, it will be interesting to see what shims come off when I get the heads back
PeterBurgess said:
How many miles have you done hard use prolonged 7K one build? At 30 hours our B valves 34.3mm ex and 43/45mm inlet ( depending on spec) will lap in but we prefer a light reface. The CI seat in the head for the inlet benefits from a tickle, the leadfree ex seat insert doesn't need recut. No visible wear on stems whether chrome/tuftride or plasma nitride treated.
Peter
FFS mine spends more time in the garage than it does at any rpm ! lolPeter
Not helped by bloody parts suppliers sending out completely the wrong stuff !
Yeah they're dished. First obvious thoughts are it's possible they've had an issue with weak valve heads in early engines and reverted to a non dish to try and stop it deforming.
Does the problem with the valve clearance tightening up exist across the years and was it worse earlier on with those valves?
Does the problem with the valve clearance tightening up exist across the years and was it worse earlier on with those valves?
Posted yesterday in Cerbera forum
Note section on loose valve guides
Note section on loose valve guides
Byker28i said:
New large main bearing crank with associated machining etc, aux shaft upgrade, converted the front crankshaft oil seal housing to the later type as the old pulley adaptor had fretted on the crank nose as the bolt had been loose with the washer missing.
The cylinder heads caused issues as the casting was oversize and oval for 2 of the valve guides, it's sugegsted these must have been loose for most of the engines life. Two of the guides fell out when the engine was dismantled.
Then it's new everything else, camshafts, valves, everything uprated to the latest spec etc.
However it's the same price I paid for the car 11 years ago...
The cylinder heads caused issues as the casting was oversize and oval for 2 of the valve guides, it's sugegsted these must have been loose for most of the engines life. Two of the guides fell out when the engine was dismantled.
Then it's new everything else, camshafts, valves, everything uprated to the latest spec etc.
However it's the same price I paid for the car 11 years ago...
My machinist requested a pair of new valves in order to check guide wear
He condemned the original valves immediately
He advised that the exhaust guides needed to be replaced, but that intakes were fine (except for the loose guide)
I had the new guides shipped directly to the machine shop
Despite appearing to be Bronze on the parts site, what was delivered was Cast Iron
So I now have Bronze intake guides and Cast Iron exhaust guides
I presume Bronze would have been better because of the exhaust valve cooling requirements
However 60k miles seems quite low mileage to require new guides so perhaps harder wearing iron is not a disaster
As for the loose guide, my machinist fitted the exhaust guides first, and did a test fit with the intake and reported that it went in perfectly first time
He said the old guide appeared to be undersized, although I didn't get to see the old guides myself
The valve seats have all been CNC cut, and I have been advised to lap the valves using fine paste only
What I have read suggests that the lapping should be done in about ten seconds each, or risk creating a concave contact area
I wonder what chance these Frankenstein heads have of lasting another 60k
Any thoughts?
He condemned the original valves immediately
He advised that the exhaust guides needed to be replaced, but that intakes were fine (except for the loose guide)
I had the new guides shipped directly to the machine shop
Despite appearing to be Bronze on the parts site, what was delivered was Cast Iron
So I now have Bronze intake guides and Cast Iron exhaust guides
I presume Bronze would have been better because of the exhaust valve cooling requirements
However 60k miles seems quite low mileage to require new guides so perhaps harder wearing iron is not a disaster
As for the loose guide, my machinist fitted the exhaust guides first, and did a test fit with the intake and reported that it went in perfectly first time
He said the old guide appeared to be undersized, although I didn't get to see the old guides myself
The valve seats have all been CNC cut, and I have been advised to lap the valves using fine paste only
What I have read suggests that the lapping should be done in about ten seconds each, or risk creating a concave contact area
I wonder what chance these Frankenstein heads have of lasting another 60k
Any thoughts?
Edited by ukkid35 on Sunday 22 July 09:51
If the guides are sintered ci they will have excellent wear rate and good heat transfer properties The heat transfer of the bronze guides and its wear resistance will depend on material.
Having said that, I think, if I ordered bronze guides, I would expect bronze guides to arrive.
Peter
Having said that, I think, if I ordered bronze guides, I would expect bronze guides to arrive.
Peter
Good call Aunteiroll, it would be unusual not to have the stems of stainless steel valves treated, whether it be hard flash chroming, tuftriding or plasma nitriding. It used to be around 50 p to have a stem treated as part of the manufacturing process, I guess it would be a couple of quid these days. I always have the stems treated come what may so have not needed to ask how much since I had my first batch of valves made in 1986 and they weren't treated, I learned very quickly about guides and valves!
The manganese silicon bronze we use, as soon as the engine starts, allows microscopic wear which leaves manganese silicide load bearing needles which are compatible and safe with all stem materials whether treated or not.
Peter
The manganese silicon bronze we use, as soon as the engine starts, allows microscopic wear which leaves manganese silicide load bearing needles which are compatible and safe with all stem materials whether treated or not.
Peter
It's my understanding that the valves are chrome plated, but that is not part of the description on the TVR Parts website
"Product Description: OE exhaust valve for the AJP V8 engine. This is a high quality exhaust valve for the AJP V8 engine from the OE UK supplier."
However, all parts are from TVR, so you would hope that they would not be incompatible
Is there any easy way to check whether the valves are plated?
When I finally install the valves, is there anything I should use to lubricate the guides? Assembly Lube?
"Product Description: OE exhaust valve for the AJP V8 engine. This is a high quality exhaust valve for the AJP V8 engine from the OE UK supplier."
However, all parts are from TVR, so you would hope that they would not be incompatible
Is there any easy way to check whether the valves are plated?
When I finally install the valves, is there anything I should use to lubricate the guides? Assembly Lube?
I test the stem, where any marks will not cause problems such as where the valve enters guide etc, with a the edge of a good file, gently increase pressure to see if you can mark it. If it doesn't easily mark it is treated. Untreated stainless stems are very soft and easily scuff. If it does scuff and I do decide to use the valves I polish the stem to ensure there are no stress risers.
I use chainsaw chain lube to oil valves as it is good and stringy and stays put for as long as the head is unused ( longest we have had a customer wait to use an engine is 10 years, it ran just so even though we had fingers crossed!).
I forgot to say, if they are flash chromed you should see where the chroming which is a little dull starts and finishes along the stem.
Peter
I use chainsaw chain lube to oil valves as it is good and stringy and stays put for as long as the head is unused ( longest we have had a customer wait to use an engine is 10 years, it ran just so even though we had fingers crossed!).
I forgot to say, if they are flash chromed you should see where the chroming which is a little dull starts and finishes along the stem.
Peter
ukkid35 said:
My machinist requested a pair of new valves in order to check guide wear
I have no idea why. Any valve has unworn sections of the stem that don't contact the valve guide that you can measure for a datum of a new valve and you can measure guide wear with seat cutting pilots. Presumably he doesn't actually do his own seat cutting.[quote=ukkid35However 60k miles seems quite low mileage to require new guides so perhaps harder wearing iron is not a disaster
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